Hazardous location compliant circuit protection devices, systems and methods with safety lockout/tagout components

ABSTRACT

Hazardous location compliant solid state circuit protection devices include safety lockout components ensuring disconnection as a safeguard in the completion of power system maintenance and service tasks by responsible personnel. The safety lockout components may include a mechanical lockout interfacing with a physical lock element, an electrical lockout implemented through the controls of the solid state circuit breaker device, and combinations thereof. Visual device feedback and confirmation may be provided to personnel that the lockouts have been successfully activated, as well as successfully deactivated to reconnect and restore operation of the load side circuitry.

CROSS REFERENCE TO RELATED APPLICATIONS

This application the benefit of U.S. Provisional Application Ser. No.62/785,007 filed Dec. 26, 2018, the complete disclosure of which ishereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION

The field of the invention relates generally to circuit protectiondevices, and more specifically to hazardous environment compliantcircuit protection devices including enhanced safety lockout featuresfor the completion of power system maintenance and service tasks.

Various different types of circuit protection devices exist to satisfythe needs of electrical power systems providing electrical power tovarious electrical loads. For example, various different devices andassemblies are known that provide disconnect functionality between apower supply circuit and an electrical load. With such devices, outputpower may be selectively switched from a power supply either manually orautomatically through such devices to facilitate service and maintenanceof the electrical power system, as well as to address electrical faultconditions. Circuit breaker devices and fusible disconnect switchdevices are two well-known types of devices that each provide adifferent capability to respond to overcurrent and electrical faultconditions and to electrically isolate load-side electrical equipmentfrom line-side power supply circuitry, thereby protecting the load-sideequipment and circuitry from otherwise damaging overcurrent conditionsin the electrical power system.

While known circuit protector disconnect devices are available thatsatisfy the needs of many electrical systems, they remain disadvantagedin some aspects for certain types of electrical systems and applicationsin which the circuit protectors are located in hazardous locations.Existing circuit protector disconnect devices therefore have yet tocompletely meet the needs of the marketplace. Improvements areaccordingly desired.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting and non-exhaustive embodiments are described with referenceto the following Figures, wherein like reference numerals refer to likeparts throughout the various drawings unless otherwise specified.

FIG. 1 is a perspective view of a compliant, hazardous location arc-lesscircuit protection device according to a first exemplary embodiment ofthe invention.

FIG. 2 is a simplified schematic diagram of the circuit protectiondevice shown in FIG. 1 in an exemplary solid state configuration.

FIG. 3 is a block diagram of the circuit protection device shown inFIGS. 1 and 2.

FIG. 4 is a front view of the circuit protection device shown in FIGS. 1through 3 and illustrating exemplary safety lockout/tagout componentstherefor.

FIG. 5 is an end view of the circuit protection device shown in FIG. 4in a disconnected state showing the safety lockout/tagout componentsengaged.

FIG. 6 is an end view of the circuit protection device shown in FIG. 4in the connected state with the exemplary safety lockout/tagoutcomponents disengaged.

FIG. 7 is an exemplary algorithmic flowchart of safety lockoutactivation and deactivation processes for the device shown in FIGS. 4-6.

FIG. 8 is a perspective view of a compliant, hazardous location arc-lesscircuit protection device according to a second exemplary embodiment ofthe invention.

FIG. 9 is a simplified schematic diagram of the circuit protectiondevice shown in FIG. 8 in an exemplary hybrid configuration.

FIG. 10 is a block diagram of the circuit protection device shown inFIGS. 8 and 9.

FIG. 11 diagrammatically illustrates thermal management features for thecircuit protection device shown in FIGS. 8 through 10.

FIG. 12 illustrates an exemplary panelboard including compliant,explosive location circuit protection devices.

DETAILED DESCRIPTION OF THE INVENTION

In order to understand the inventive concepts described herein to theirfullest extent, set forth below is a discussion of the state of the artas it relates to issues posed by hazardous locations, followed byexemplary embodiments of devices, systems and methods addressing suchissues and meeting longstanding but unfulfilled needs in the art.

I. State of the Art

Electrical power systems sometimes operate within hazardous environmentspresenting a risk of explosion via ignition of a surrounding gas orvapor dusts, fibers, or flyings. Such hazardous environments may arisein, for example only, petroleum refineries, petrochemical plants, grainsilos, wastewater and/or treatment facilities among other industrialfacilities, wherein volatile conditions are produced in the ambientenvironment and present a heightened risk of fire or explosion. Atemporary or sustained presence of airborne ignitable gas, ignitablevapors or ignitable dust, or otherwise flammable substances presentssubstantial concerns regarding safe and reliable operation of suchfacilities overall, including but not limited to safe operation of theelectrical power system itself, which in some instances by virtue ofconventional circuit protector devices may produce ignition sources innormal operation and in the presence of an electrical fault. As such, anumber of standards have been promulgated relating to electrical productuse in explosive environments to improve safety in hazardous locationsin view of an assessed probability of explosion or fire risk.

For example, Underwriter's Laboratories (“UL”) standard UL 1203 setsforth Explosion-Proof and Dust-Ignition-Proof Electrical Equipmentcriteria for hazardous locations. Explosion-Proof andDust-Ignition-Proof enclosures are presently available to enclose orcontain electrical products, including but not necessarily limited tocircuit protection devices that are not themselves Explosion-Proof orDust-Ignition-Proof. In combination with appropriate Explosion-Proof andDust-Ignition-Proof enclosures, electrical equipment manufacturers mayreceive UL certification of compliance with the applicable ratingstandards for hazardous locations, and UL certification is an importantaspect of a manufacturer's ability to successfully bring products tomarket in North America or any other market accepting of UL standard UL1203.

The National Electric Code (NEC) generally classifies hazardouslocations by class and division. Class 1 locations are those in whichflammable vapors and gases may be present. Class II locations are thosein which combustible dust may be found. Class III locations are thosewhich are hazardous because of the presence of easily ignitable fibersor flyings. Considering Class 1, Division 1 covers locations whereflammable gases or vapors may exist under normal operating conditions,under frequent repair or maintenance operations, or where breakdown orfaulty operation of process equipment might also cause simultaneousfailure of electrical equipment. Division 1 presents a greater risk ofexplosion than, for example, Division 2 where flammable gases or vaporsare normally handled either in a closed system, confined within suitableenclosures, or are normally prevented by positive mechanicalventilation.

The International Electrotechnical Commission (IEC) likewise categorizeshazardous locations into Zone 0, 1, or 2 representing locations in whichflammable gases or vapors are or may be airborne in an amount sufficientto produce explosive or ignitable mixtures. As defined in the IEC, aZone 0 location is a location in which ignitable concentrations offlammable gases or vapors are present continuously or for long periodsof time. A Zone 1 location is a location in which ignitableconcentrations of flammable gases or vapors are likely to exist or mayexist frequently because of repair or maintenance operations or becauseof leakage or possible release of ignitable concentrations of flammablegases or vapors, or that is adjacent to a Zone 0 location from whichignitable concentrations of vapors could be communicated.

Given that electrical devices, such as those described below, can beignition sources in certain circumstances, explosion-proof, flame-proof,or ignition proof enclosures are conventionally provided in NEC Division1 or 2 locations and/or IEC Zone 1 or 2 locations to house electricaldevices that otherwise pose ignition risk. The terms “explosion-proof”or “flame-proof” in this context, refer to enclosures that are designedto be capable of containing an internal explosion of a specifiedflammable vapor-air mixture. In addition, the explosion-proof orflame-proof enclosure must operate at a safe temperature with respect tothe surrounding atmosphere.

Conventional circuit breaker devices, switch devices of various types,and contactor devices are known to include input terminals connectableto power supply or line-side circuitry, output terminals connectable toone or more electrical loads, and pairs of mechanical switch contactsbetween the respective input terminals and output terminals. Each pairof mechanical switch contacts typically includes a stationary contactand a movable contact linked to an actuator element that displaces themovable contact along a predetermined path of motion towards and awayfrom the stationary contact to connect and disconnect a circuit paththrough the device and to therefore electrically connect or disconnectthe input and output terminals. When the switch contacts are opened, thedevice serves to isolate the electrical load(s) connected to the outputterminals from the power supply connected to the input terminals. Theactuator element in the mechanical switch devices described above may beautomatically movable for circuit protection purposes to open themechanical switch contacts in response to overcurrent or faultconditions in the line-side circuit and electrically isolate theelectrical load(s) from electrical fault conditions to prevent them frombeing damaged, or the actuator element may be manually movable toelectrically isolate the electrical loads from the line-side powersource for energy conservation, maintenance of the load, etc.

Circuit breakers and fusible disconnect switch devices are twowell-known types of devices that each provide a different type ofdisconnect functionality and circuit protection via mechanical switchcontacts. The IEC includes the following pertinent definitions:

2.2.11

Circuit-Breaker

-   -   mechanical switching device, capable of making, carrying and        breaking currents under normal circuit conditions and also        making, carrying for a specified time and breaking currents        under specified abnormal circuit conditions such as those of        short circuit [441-14-20]

2.2.9

Switch (Mechanical)

-   -   mechanical switching device capable of making, carrying and        breaking currents under normal circuit conditions which may        include specified operating overload conditions and also        carrying for a specified time currents under specified abnormal        circuit conditions such as those of short circuit [441-14-10]        NOTE A switch may be capable of making but not breaking        short-circuit currents.

2.2.1

Switching Device

-   -   device designed to make or break the current in one or more        electric circuits [441-14-01] NOTE A switching device may        perform one or both of these operations.

It is seen from the definitions above that the circuit breaker asdefined in IEC 2.2.11 and the mechanical switch as defined in IEC 2.2.9differ in their capability to mechanically respond to abnormal circuitconditions. Specifically, the circuit breaker, as defined in IEC 2.2.11,can mechanically break short circuit conditions, whereas the mechanicalswitch as defined in IEC 2.2.9 cannot. Because of this, an electricalfuse is sometimes used in combination with the mechanical switch of IEC2.2.9 to realize a fusible disconnect switch that can respond to a shortcircuit condition via operation of the fuse (i.e., an opening of thefuse) rather than operation of the mechanical switch contacts.

In either of the devices of IEC 2.2.11 and 2.2.9, the automatic circuitprotection may sometimes be provided solely via the structural designand calibration of the circuit breaker structure or the structure of thefuse element(s) in the fuse, provided that each realizes predeterminedtime-current characteristics before opening of the circuit. The NEC hasdefined these two basic types of Overcurrent Protective Devices (OCPDs)as follows:

-   -   fuse—An overcurrent protective device with a circuit-opening        fusible part that is heated and severed by the passage of        overcurrent through it.    -   circuit breaker—A device designed to open and close a circuit by        nonautomatic means and to open the circuit automatically on a        predetermined overcurrent without damage to itself when properly        applied within its rating.        The NEC also requires that circuits be provided with a        disconnecting means, defined as a device, or group of devices,        or other means by which the conductors of a circuit can be        disconnected from their source of supply. Since fuses are        designed to open only when subjected to an overcurrent, fuses        generally are applied in conjunction with a separate        disconnecting means (NEC Article 240 requires this in many        situations), typically some form of a disconnect switch. Since        circuit breakers are designed to open and close under manual        operation, as well as in response to an overcurrent, a separate        disconnecting means is not required.

In some types of circuit protection devices, automatic circuitprotection may be realized via electrical sensors included in the deviceto monitor actual circuit conditions and, in response to predeterminedcircuit conditions as detected by the sensors, electromechanical tripfeatures may be actuated to automatically open the movable contacts inresponse to detected overcurrent conditions including overload and shortcircuit conditions. Once tripped, the circuit breaker may be reset orreclosed to restore affected circuitry through the switch contacts, asthe circuit breaker is designed to open the circuit without damage toitself, whereas a fuse opens a circuit via internal degradation of thefuse element(s) to the point where they can no longer carry electricalcurrent. As such, the fuse must be replaced after opening to restoreaffected circuitry. Combinations of circuit breakers and fuses are alsodesirable in some instances, with selective coordination thereof, toextend the range of overcurrent conditions that may be addressed as wellas to improve response times.

In contrast to the circuit protection devices described above, the“switching device” of IEC 2.2.1 as defined above refers merely to themaking and breaking of current, without any reference to making orbreaking overcurrent conditions (i.e., overload conditions or shortcircuit conditions). The “switching device” of IEC 2.2.1 thereforeprovides a disconnect function, but not a circuit protection function.IEC 2.2.1 also does not require a mechanical switching device at all,but to the extent that a switch device that is not a circuit breakerdevice actually includes mechanical switch contacts, it couldnonetheless present an ignition risk when located in hazardousenvironments.

More specifically, an operation of mechanical switch contacts to make orbreak an energized circuit, whether manually actuated by a user undernormal circuit conditions or automatically actuated under abnormalcircuit conditions, presents a possible ignition source in a hazardousenvironment. Specifically, as the movable contacts are mechanicallydisplaced away from stationary contacts (i.e., moved from a closedposition to an opened position), electrical arcing between the switchcontacts tends to result. Similar arcing may occur as the movablecontacts are moved back towards the stationary contacts to reclose thedevice. If such arcing between the switch contacts is realized in thepresence of a combustible gas, vapor or substance, the arcing may ignitethe gas, vapor or substance. While the mechanical switch contacts aretypically enclosed in housings provided with conventional circuitbreakers or other mechanical switch devices as well as additionalenclosures commonly utilized with panelboards or motor control centers,etc., such housings and enclosures are typically not sufficient toisolate electrical arcing from ignitable, airborne elements. For thisreason, known devices including mechanical switch contacts areconventionally located in individual explosion-proof enclosures andagain contained in an environmental enclosure, or a system of switches(i.e., a panelboard) that can in turn be installed in a single largeexplosion-proof enclosure without individual explosion-proof enclosuresfor the switches provided within an NEC Division 1 location to providethe necessary protection.

Of the devices described thus far, circuit breakers, while mechanicallybreaking a short circuit condition, experience the most intense arcingconditions and therefore have the greatest potential in terms of rawenergy and temperature to ignite combustible gases, vapors or substancesin a hazardous location. Considering that many industrial power systemsand loads operate at relatively high voltage and high current, arcenergy and temperatures in lower current overload conditions and normalconditions is likewise considerable and therefore poses ignition risks.In general, ignition energy resulting from the fault energy is relatedto the magnitude of the current being interrupted, so the higher thecurrent being interrupted the greater the arcing potential and severity.For example, a65kAIC interruption is much more significant from thearcing perspective, and hence more hazardous, than a 10kAIC interruption

Available explosion-proof, flame-proof or ignition-proof enclosures areeffective to provide safe operation of mechanical switch devices in anNEC Division 1 or 2 location or an IEC Zone 1 or 2 location, butgenerally impart additional costs, occupy valuable space in theelectrical power system, and impose certain burdens to the installationand servicing of an electrical power system over time. Obtaining accessto the disconnect devices inside the explosion-proof enclosurestypically requires a time-consuming removal of a number of fasteners,and after any maintenance procedures are completed all the fastenersmust be properly replaced to ensure the desired safety of theexplosion-proof enclosure. During maintenance procedures, the area inwhich the disconnect devices are located are also typicallydecommissioned (i.e., disconnected) with associated load-side processesshut down to ensure safety during the maintenance procedure. Suchdecommissions are costly from the perspective of the industrial facilityand limiting or shortening decommissioned downtime is important. Itwould therefore be desirable in some cases if the explosion-proofenclosures could be eliminated in an NEC Division 1 location while stillproviding safe disconnect functionality in hazardous environments. Inorder to do so, circuit protection devices designed to reduce ignitionrisks are needed, but at present generally do not exist.

Solid state disconnect devices are known that provide desirabledisconnect functionality via semiconductor switches or semiconductordevices such as, but not limited to, insulated-gate bipolar transistors(IGBTs), Metal Oxide Semiconductor Field Effect Transistors (MOSFETs)and other known elements that electronically operate in a known mannerto preclude current flow through the device and therefore electricallyisolate line-side circuitry from load-side circuitry in response topredetermined circuit conditions without utilizing mechanical switchcontacts. Such solid state switches may be implemented in circuitbreaker devices or used in combination with fuses to address electricalfault conditions in an automatic manner.

Solid state switches beneficially eliminate electrical arcing associatedwith displacement of mechanical switch contacts as described above, butnonetheless still present possible ignition sources via heat generatedby the solid state switches in use. Depending on the type andconcentration of combustible elements in the hazardous location, thesurface temperature of the solid state switch devices may rise to thepoint where spontaneous ignition may occur due to the flash temperatureof the specific gas or ignitable substance in the hazardous location,even though no arcing occurs in the switching operation of the device.

Connecting terminals of solid state switch devices may also presentreliability issues and possible ignition sources when used in an NECDivision 1 or 2 location or an IEC Zone 1 or 2 location. Morespecifically, the terminals may tend to loosen over time when subjectedto thermal cycling or vibration. Loose terminal connections may causeoverheating and possible ignition sources at the locations of theterminals, if not electrical arcing, under certain operating conditions.Poor quality terminal connections may also cause overheating of theconductor structure (sometimes referred to as the bus) in the device,presenting still further ignition concerns in hazardous locations. Assuch, the use of known solid state switching devices, without more, doesnot itself ensure sufficient safety in hazardous locations withoutcomplementary use of an explosion-proof enclosure in NEC Division 1 or 2locations or IEC Zone 1 or 2 locations.

So-called hybrid disconnect devices are also known that include acombination of semiconductor switches or semiconductor devices andmechanical switch contacts. Such hybrid devices may likewise beimplemented in circuit breaker devices or used in combination with fusesto address electrical fault conditions in an automatic manner. Hybriddisconnect devices present a mix of the issues discussed above from theperspective of possible ignition sources in a hazardous location, andadequate safety in the absence of a complementary use of anexplosion-proof enclosure in NEC Division 1 or 2 location or IEC Zone 1or 2 locations cannot be ensured.

II. Inventive Arc-less Devices, Systems and Methods for HazardousLocation Compliance.

Exemplary embodiments of circuit protection devices are described hereinthat overcome the problems above and that provide an enhanced degree ofsafety for compliance with the applicable standards in NEC Division 1 or2 location or an IEC Zone 1 or 2 location without necessarily requiringa separately provided explosion-proof, flame-proof or ignition-proofenclosure. As such, and via the elimination of separately providedexplosion-proof, flame-proof or ignition-proof enclosures, the exemplarycircuit protection devices described herein may be implemented in anelectrical power system at reduced cost and in a reduced amount of spacein electrical panels, control centers, and the like. The exemplarycircuit protection devices described herein may be provided in a modularand configurable system that facilitates a more economical installation,maintenance and oversight of the electrical power system. Method aspectswill be in part explicitly discussed and in part apparent from thefollowing description.

In a first aspect, exemplary circuit protection devices may beimplemented in the form of a solid state circuit protection devicehaving arc-less operation in switching of the device to connect ordisconnect load-side circuitry through the solid state switch device, incombination with enhanced features to address possible ignition sourcesat the connection terminals, and/or including thermal managementfeatures to address potential overheating of conductive elementsinternal to the solid state switch device. When implemented in the formof a solid state circuit breaker device, such solid state circuitbreakers, unlike conventional circuit breakers, therefore comply withhazardous location standards applicable to NEC Division 1 or 2 locationsor IEC Zone 1 or 2 locations and thus render conventionalexplosion-proof, flame-proof or ignition-proof enclosures obsolete forcertain applications.

In a second aspect, exemplary hazardous location compliant solid statecircuit breaker devices may be provided with a safety lockout/tagoutmode that ensures disconnection through the solid state circuit breakerdevices as a safeguard in the completion of power system maintenance andservice tasks by responsible personnel. In different embodiments, thesafety lockout/tagout mode may feature a mechanical lockout interfacingwith a physical lock element, an electrical lockout implemented throughthe electronic controls of the solid state circuit breaker device, andcombinations thereof. Visual device feedback and confirmation may beprovided to personnel that lockout conditions have been successfullyactivated to disconnect the load-side circuitry so that workers maysafely proceed to perform the applicable maintenance or serviceprocedures on the load-side of the device in a safe manner. Visualfeedback and confirmation may be likewise provided to personnel that thelockouts have been successfully deactivated to complete a tagoutprocedure and reconnect and restore operation of the load sidecircuitry.

In a third aspect, a hybrid circuit protection device may be implementedin the form of a combination solid state switching device and amechanical switch device, and further in combination with enhancedfeatures to isolate electrical arcing between the mechanical switchcontacts from the ambient environment to prevent ignition, as well asaddressing possible ignition sources at the connection terminals and/orincluding thermal management features to avoid potential overheating ofconductors in the hybrid device. Such hybrid circuit protection devices,unlike conventional hybrid circuit protection devices, therefore complywith hazardous location standards applicable to NEC Division 1 or 2locations or IEC Zone 1 or 2 locations and render conventionalexplosion-proof enclosures obsolete for certain applications.

In a fourth aspect, exemplary hazardous location compliant hybridcircuit protection devices may be provided with a safety lockout/tagoutmode that ensures disconnection through the hybrid circuit protectiondevices as a safeguard in the completion of power system maintenance andservice tasks by responsible personnel. In different embodiments, thesafety lockout mode may feature a mechanical lockout interfacing with aphysical lock element, an electrical lockout implemented through thecontrols of the solid state circuit breaker device, and combinationsthereof. Visual device feedback and confirmation may be provided topersonnel that the lockout conditions have been successfully activatedto disconnect the load-side circuitry so that workers may safely proceedto perform the applicable maintenance or service procedures on theload-side of the device in a safe manner. Visual feedback andconfirmation may be likewise provided to personnel that the lockoutshave been successfully deactivated to complete a tagout procedure andreconnect and restore operation of the load side circuitry.

While the following discussion is made in the context of circuit breakerdevices, the inventive concepts below are not necessarily limited tocircuit breaker devices and instead may broadly accrue to other types ofdevices, examples of which are discussed above, that present similarissues from the perspective of ignition concerns in a hazardouslocation. Likewise, while the inventive concepts are described in thecontext of hazardous locations such as NEC Division 1 and 2 locations orIEC Zone 1 or 2 locations, the benefits of the concepts described arenot necessarily limited to NEC Division 1 or 2 locations or IEC Zone 1or 2 locations and instead may more broadly apply to other types ofhazardous environments, and in some aspects may be beneficially providedfor use in non-hazardous locations as desired.

FIG. 1 is a perspective view of a compliant, hazardous environmentcircuit protection device 100 according to a first exemplary embodimentof the invention. The circuit protection device 100 includes a housing102 having opposing longitudinal sides 104, 106 and opposing lateralsides 108, 110 arranged generally orthogonally with respect to thelongitudinal sides 104, 106. The housing 102 also includes a front side112 and a rear side 114, and the front side 112 may include an optionaldigital display 116 that functions as a user interface for the device100. As shown the display 116 visually indicates voltage, current, powerand energy readings to a person in the vicinity of the device 100 anddisplay 116.

The housing 102 of the device 100 is fabricated from strategicallyselected or otherwise custom formulated materials to withstand allpossible electrical operating conditions, and specifically all possibleelectrical fault conditions including simultaneous fault conditions thatmay be presented by the electrical power system being protected in a NECDivision 1 or 2 location or an IEC Zone 1 or 2 location.

For compliance in an NEC Division 1 location or an IEC Zone 1 or 2location, the housing structure and housing material must likewise befurther formulated to provide adequate strength to withstand shock andimpact forces that may be realized in an explosive environment, as wellas to provide chemical resistance to withstand exposure to chemicals inthe explosive environment that could otherwise negatively impact theintegrity of the device 100. As used herein, “chemical resistance”refers to the strength of the housing material to protect againstchemical attack or solvent reaction. Chemical resistance in the housing102 is the opposite of chemical reactivity that may cause an undesirablechemical effect when the housing 102 is exposed to certain chemicalsand/or that my undesirably generate heat and raise the temperature ofthe housing 102. Chemical resistance, via little or no reactivity tospecified chemicals, relates to the resistivity of the housing 102 tocorrosive or caustic substances in the environment, including but notlimited to airborne gases and vapors. For the device 100, chemicalresistance is important to all materials and structure that contributesto the hazardous location compliance described herein.

UL 1203 defines chemical testing that may be applied to determinewhether any formulation of a candidate material for the housing 102 ischemically resistant for explosive environment locations. Specifically,UL 1203 chemical testing requires sample housings to be fabricated fromthe formulation of candidate material in the housing structure desired,and a lengthy exposure of the sample housings to saturated vapors in theair including a number of specified chemicals for a predetermined periodof time. The specified chemicals for UL 1203 chemical testing includeacetic acid, acetone, ammonium hydroxide, ASTM reference fuel C, diethylether, ethyl acetate, ethylene dichloride, furfural, n-hexane, methylethyl ketone, methanol, 2-nitropropane, and toluene. Different samplehousings are exposed to each chemical for a predetermined period oftime, and after exposure to each chemical, the sample housings areinspected to ensure that the housing structure of the samples is notcompromised or shows signs of degradation via, for example,discoloration, swelling, shrinking, crazing, cracking, leaching, ordissolving. Sample housings that pass inspection are then subjected to acrush test and compared to the results of crush testing prior to thechemical exposure. If the crushing force of the chemically tested samplehousings shows that the chemically tested sample housings withstand atleast 85% of the corresponding crush force as tested prior to thechemical exposure, the sample housings are UL 1203 compliant.

The housing 102, via the material from which it is fabricated, shouldlikewise exhibit chemical compatibility with specific chemicals presentin a given NEC Division 1 or 2 location or an IEC Zone 1 or 2 location.Chemical compatibility refers to the stability of the housing whenexposed to substances in the hazardous location environment. If thehousing 102 chemically reacts to a substance in the environment, it isconsidered incompatible. Accordingly, compatibility testing isnonetheless advisable to confirm chemical compatibility in view of thenumber of different corrosive or caustic chemicals and substances usedacross the spectrum of industrial facilities. Different facilitiesinvolving different caustic or corrosive substances may demand housingsof different materials to address issues presented. Strategic selectionand custom formulation of housing materials may be needed for someexplosive environments if a universally optimal housing or materialformulation cannot be practically determined or economically provided.In some cases, UL 1203 compliance for the housing may obviate a need forchemical compatibility testing in selected facilities, and chemicalcompatibility testing may accordingly be considered optional.

The material used to fabricate the housing 102 may likewise bestrategically selected or otherwise formulated, as well as formed withspecific structure, to achieve thermal management and surfacetemperature goals for the device 100 in operation. Some housingmaterials may exhibit better thermal performance to distribute anddissipate heat than other materials. For example, specific polymericresins may be selected or customized, and formulated or processed torealize a housing 102 that will improve thermal performance of thedevice 100 in use when protecting the electrical power system, bothinternally to the housing 102 and on its outer surface area such thatthe outer surface area temperature is maintained at a level below thetemperature which could cause ignition in an NEC Division 1 or 2location or an IEC Zone 1 or 2 location.

For any given housing material, the shape and form factor of the housing102, including dimensions, contours, etc. may vary the overall thermalperformance and surface temperature positively or negatively. Forinstance, for a given device rating and operating voltage and current ofthe electrical power system, a housing having a larger outer surfacearea will generally reduce surface temperature in use as compared to ahousing having a smaller outer surface area. The housing structure canbe designed to optimize and balance overall package size andconfiguration with thermal performance.

In some embodiments, the housing 102 may be fabricated from metal ormetal alloys, non-metallic insulative materials such as high strength,high performance plastics, or combinations of metallic and non-metallicmaterials to vary thermal performance and the other considerationsabove, namely impact resistance and chemical resistance. Encapsulatedhousing constructions, in whole or in part, are likewise possible. Insome instances, the interior of the housing 102 may likewise be filledin whole or in part with dielectric material, dielectric fluid, pottingmaterials, or other filler media such as sand to contain, absorb ordissipate heat and energy of energized electrical conductors and switchcomponents in the device 102 to unsure that the surface temperature ofthe housing 102 will remain below a selected target temperature toprovide a device 100 having a desired temperature classification ortemperature rating.

Apart from the materials utilized in its fabrication, the structure ofthe housing 102 could likewise be designed with heat distribution anddissipation in mind. The housing can be structured strategically toinclude more than one housing material throughout or at specificallytargeted locations in the housing 102. Housing sub-structures could beindependently fabricated and provided for assembly to provide additionalthermal insulation or thermal conductivity in desired areas of thehousing to selectively confine and distribute heat in a strategic mannerin select locations. Wall thickness of the housing 102 could likewise bevaried to provide greater or lesser degrees of thermal conductivity andheat dissipation in selected portions of the structure or in certainareas of the housing structure at the most desirable locations. Piping,channels, or pockets may be formed to strategically capture generatedheat and direct it more efficiently to desired locations fordissipation. Heat sink materials and the like may be included to improvethermal absorption and dissipation.

Active cooling elements are likewise possible in which cooling fluidsare passed over or through the housing structure, with the housingstructure including appropriate structure to facilitate active cooling.Active cooling elements could be self-contained or separately providedsuch as in a panelboard application where a number of devices 100 may beprovided, with an active cooling system countering the cumulativegeneration of heat in closely positioned devices 100 and alleviatingtemperature effects that the devices 100 may have upon one another. Theactive cooling system may include cooling fans or pumps which circulatefluids in or around a number of devices 100 to effectively managesurface temperatures. The devices 100 including temperature sensors 158(FIG. 3) may provide feedback signals to an active cooling system topower on when needed and otherwise be powered off Thermal electrics mayalso be deployed as may feedback loops with the load equipment to reduceavailable current through the device (thereby reducing heat).

The above thermal management considerations may be pursued in variousdifferent combinations, some of which may counteract or obviate a needfor other of the considerations. For example, active cooling in someapplications may obviate a need for certain features of the housingdescribed, such as a more sophisticated shape and form factor todissipate heat over a relatively complex surface area.

The lateral sides 108, 110 of the housing 102 each include connectionrecesses 118, 120, 122 for respective connection to line-side andload-side circuitry. In the example shown in FIG. 1, three connectionrecesses 118, 120, 122 are provided for respective connection to a threephase power supply on one of the sides 108, 110 and to three phaseload-side equipment on the other. The power supply and load may eachoperate with alternating current (AC) or direct current (DC). The device100 as shown is configured as a circuit breaker and therefore providesautomatic circuit protection in response to predetermined overcurrentconditions, which may be selected by the user within a certain rangeinput to the device 100 via the display screen 116, via another userinterface including a remote interface, and/or pre-programmed into thedevice. The device 100 may operate according to specified time-currentcurves or trip profiles suitable to provide adequate protection forconnected loads.

The display 116 may be multi-functional to display different screens inresponse to user activation. In some embodiments the display 116 may betouch sensitive with the user making selections via touching selectedareas of the display as prompted. Input selectors such as buttons,knobs, etc. may be separately supplied from the display 116 forinteractive by a user in relation to the display. An input selector suchas a toggle switch may also be provided separately from the display 116to serve as manually operable on/off switches that may intuitively bemanually operated by a user. In this case, the toggle switch may emulatea traditional toggle switch to affect a change of state to “on” or“off”, it may do so without displacement of mechanical switch contactsbecause, as explained below, the device 100 does not include mechanicalswitches. Alternatively, an on/off feature may be built into the display116 for convenient use by an operator to achieve disconnect switchfunctionality to connected load side equipment.

The display 116 may be multi-functional to display different screens inresponse to user activation. In some embodiments the display 116 may betouch sensitive with the user making selections via touching selectedareas of the display as prompted. Input selectors such as buttons,knobs, etc. may be separately supplied from the display 116 for userinput in relation to prompts or information presented on the display116. It is recognized, however, that the display or array of displays116 can be considered optional in certain embodiments and need not beincluded at all. In further embodiments, additional input/outputelements may be provided, whether in the form of a display or otherinterfaces for user interaction with the device both locally andremotely.

FIG. 2 is a simplified schematic diagram of the circuit protectiondevice 100 in an exemplary solid state configuration. The device 100includes input terminals 130 a, 130 b, 130 c each connected to one phaseof a three phase power supply indicated as line-side circuitry 132 inFIG. 2 via connecting cables, conduits, or wires. The device 100 furtherincludes output terminals 134 a, 134 b, 136 c each connected toload-side circuitry 136 such as motors, fans, lighting devices, andother electrical equipment in an industrial facility wherein ignitablegas, vapors or substances may be airborne as indicated at 138. Theoutput terminals 134 a, 134 b, 136 c may likewise connect to theelectrical loads via connecting cables, conduits, or wires. Optionally,the device 100 may further include additional elements such as auxiliarycontacts and auxiliary connections, shunt trip features, undervoltagerelease features, communication ports and communication elements, powerports for communication and other purposes, etc.

In between each pair of input terminals 130 a, 130 b, 130 c and outputterminals 134 a, 134 b, 136 c are solid state switch devices arranged asindicated at 140 a, 140 b and 140 c. The exemplary arrangement includesseries connected pairs of insulated-gate bipolar transistors (IGBTs) 142a, 142 b, 142 c, 142 d respectively connected in reverse to one another,with each pair of IGBTs 142 a and 142 b and 142 c and 142 d including avaristor element 144 connected in parallel to the IGBTs. The reversedconnected IGBTs in each pair precludes reverse current flow through theIGBTs from the load-side circuitry 136 to the line-side circuitry 132 ina known manner.

The IGBTs 142 a, 142 b, 142 c, 142 d are one form of a semiconductorswitch that is operable to either permit current flow between therespective input and output terminals 130 a and 134 a, 130 b and 134 b,and 130 c and 134 c from the line-side circuitry 132 to the load-sidecircuitry 136 or to preclude current from flowing through the device 100such that the load-side circuitry 136 becomes electrically isolated fromthe line-side circuitry 132. Briefly, a positive voltage applied fromthe emitter to gate terminals of the IGBT causes electrons to be drawntoward the gate terminal across a body region thereof. If thegate-emitter voltage is at or above a threshold voltage, enoughelectrons are drawn toward the gate to form a conductive channel acrossthe body region, allowing current to flow from the collector to theemitter. If the gate-emitter voltage is below the threshold voltageessentially no current can flow across the body region, such that bycontrolling the gate-emitter voltage current flow between the input andoutput terminals may be enabled or disabled to connect or disconnect theoutput terminals from the input terminals of the device 100 via theIGBTs. Equivalent types of semiconductor switch elements other than IGBTelements may likewise be employed, including, but not limited to, MetalOxide Semiconductor Field Effect Transistor (MOSFET) elements, bipolartransistor elements, silicon controlled rectifier elements (sometimesreferred to as thyristors), and the like. The number of semiconductorswitch elements may be varied to be greater or less than the numbershown in FIG. 2.

The varistor elements 144, connected in parallel to each pair of IGBTsin the arrangement shown, exhibit a relatively high resistance whenexposed to a normal operating voltage, and a much lower resistance whenexposed to a larger voltage, such as is associated with over-voltageconditions and/or electrical fault conditions. The impedance of thecurrent paths through the varistors 144 are substantially lower than theimpedance of the IGBTs when the varistors 144 operate in a low-impedancemode, and is otherwise substantially higher than the impedance of theIGBTs. This means that in normal conditions the high impedance of thevaristors 144 causes all of the current to flow through the IGBTs, butas over-voltage conditions arise the varistors 144 switch from the highimpedance mode to the low impedance mode and shunt or divertover-voltage-induced current surges away from the IGBTs to the load-side136. As over-voltage conditions subside, the varistors 144 may return toa high impedance mode. The varistors 144 beneficially allow, forexample, motor inrush currents to flow through the device 100 whileotherwise permitting the IGBTs to respond to overcurrent conditionsafter motor starting is complete. In other applications, however, thevaristors may be considered optional and may be omitted.

As a further thermal management feature, the solid state switch devices(e.g., the IGBTs) in each arrangement 140 a, 140 b and 140 c may beencapsulated with a strategically selected or otherwise formulatedmaterial to improve thermal performance of the switch devices 140 a, 140b and 140 c and/or improve heat dissipation and distribution in use. Theencapsulation material of the solid state switch devices 140 a, 140 band 140 c may be the same or different from encapsulation materialsincluded in the housing construction, and specifically are targeted tocontrol or limit the operating temperature of the silicon in the solidstate switch devices in normal circuit operation or in overcurrentconditions and electrical fault conditions to prevent overheating of theswitch devices themselves or overheating of the housing 102.

While exemplary solid state switching arrangements are shown anddescribed, others are possible to achieve solid state switchingfunctionality in an arc-less manner. As discussed above, the solid stateswitching devices avoid the type of arcing that mechanical switchesproduce, and therefore avoid such arcing from being a possible ignitionsource in NEC Division 1 or 2 locations or IEC Zone 1 or 2 locations.

In view of the hazardous environment in which the device 100 is to beused, reliable termination of line-side and load-side cables to theinput and output terminals is important as loose connections cangenerate heat and reliability issues, as well as possible ignitionconcerns in a hazardous location. In an NEC Division 2 or IEC Zone 1 or2 location, the input and output terminals may be accessible from theexterior of the housing 102. Locking terminal connection assemblies andspring-biased terminal assemblies may be utilized to accept and retainends of the respective cables, while reducing any tendency of the cableconnections to loosen over time. Depending on the specific end use ofthe device 100 and its operating conditions, such locking terminalassemblies and spring-biased terminal connectors may, however, beconsidered optional in NEC Division 2 or IEC Zone 1 or 2 locations.

In an NEC Division 1 location, the input and output terminals mayfurther be enclosed in additional housing portions to provide additionalsafety assurance. Such housing portions may be separately provided fromthe housing 102 or may be integrally formed as extensions of the housing102 to isolate the input and output terminals from the explosiveenvironment. In contemplated embodiments, removable cover elements maybe provided to access the input and output terminals and completeelectrical connections to the input and output terminals inside theenclosures of the housing portions. The line-side and load-side cableconnections may further be established, for example, via armored cableand cable glands providing ingress protection, sealing and grounding tosafely pass a line-side cable or load-side cable through the enclosuresof each housing portion. When used with armored cable, a ground to earthpath may be established via the cable gland. Armored cable is notnecessary in all embodiments, however, and may not be used. Cable glandsmay be used with non-armored cable as well.

The housing 102 may be designed and fabricated with thermal managementissues in mind to maintain surface temperatures below applicable limitsfor a given installation in an NEC Division 1 location, and in someembodiments the housing 102 may in whole or in part be explosion-proofin compliance with applicable standards for hazardous locations, albeitwith relatively smaller and more economical housing to provide than aconventional, larger and separately provided explosion-proof enclosurethat would conventionally contain the entire circuit protection device.The housing 102 and any enclosures defined therein may likewise includevacuum chambers or may filled with dielectric fluid, dielectric materialor inert gas to reduce or impede electrical arcing at the terminal/cableinterface or at other locations in the housing.

To address possible static electricity charge buildup, which presents apossible ignition source in an NEC Division 1 location, the housing 102is shown in FIG. 2 with connection to electrical ground 146. Briefly,static electricity is the result of an electromagnetic imbalance betweennegative and positive charges in an object. Charging of the housingsurface may arise via surface charge involving another object,particularly for insulative portions of the housing, or via chargeinduction for electrically conductive portions of the housing. Surfacecharging can also occur during exposure to a high voltage DC powersupply, which will cause ions to adhere to the housing surface.

Regardless of how surface charging actually arises, the connection toground 142 allows any electrical charge buildup on the housing 102 tosafely dissipate without creating an ignition source incombustible/hazardous areas. The housing 102 may be grounded to earthground or chassis ground via a line wire or line conductor connected tothe housing 102 on its outer surface. As such, any charging of theexterior of the housing 102 will be quickly dissipated as electricalcurrent to ground and obviate a high voltage discharge event, typicallyvia a spark or shock that could be generated by a person or toolutilized by a person, that could otherwise occur in the presence of theexplosive atmosphere and cause ignition.

The housing 102 itself could also be fabricated in whole in part fromantistatic polymers or antistatic materials that are weakly conductiveto electricity from the perspective of charge buildup, but nonethelessconsidered insulative and non-conductive from the perspective of theelectrical power system that the device 100 is protecting. Antistaticmaterials may improve the housing performance relative to non-antistaticmaterials by reducing any tendency of the housing to charge in the firstinstance, and this is another consideration for strategically selectingor otherwise formulating the material(s) to be utilized in the housingfabrication. Anti-static coatings, encapsulants, or shells may beprovided on the housing outer surface if desired, although chemicalresistance and compatibility must still be ensured as discussed above.When the device 100 directly connects to an enclosure/system groundplane in an actual installation, dedicated ground conductors to addressstatic electricity issues may not be necessary due to mechanicalattachment and/or physical proximity to the ground plane.

While a single ground connection is shown in FIG. 2, more than oneground connection could be provided in the structure of the device 100at any desired location. Grounding conductors may be provided interiorto the device housing 102 in addition to or in lieu of a groundingconductor connecting to the exterior of the device housing 102 asdescribed. Ground connections for the housing 102 also could beestablished via a cable connector such as a cable gland when armoredcable that already includes a ground path to earth is utilized to makethe line-side and load-side connections to the terminals 130 a, 130 b,130 c of the device 100. Of course, in some cases, non-armored cablecould be used, with or without cable glands, while still eliminatingignition sources in the device 100 and addressing static electricitywith an alternative ground connection.

In NEC Division 2 or IEC Zone 1 or 2 locations, the device 100 wouldtypically be protected by an enclosure and therefore would not be asprone to static electricity issues and discharge events. As such, theconnection to ground 146 may or may not be necessary or desirable in adevice 100 for use in an NEC Division 2 location or IEC Zone 1 locationand could therefore be considered optional. By virtue of the device 100,however, the enclosure containing one or more devices 100 need not beexplosion-proof and the conventionally provided explosion-proofenclosure may be omitted.

FIG. 3 is a block diagram of the circuit protection device 100. Thedevice 100 includes a processor-based microcontroller including aprocessor 150 and a memory storage 152 wherein executable instructions,commands, and control algorithms, as well as other data and informationrequired to satisfactorily operate the device 100 are stored. The memory152 of the processor-based device may be, for example, a random accessmemory (RAM), and other forms of memory used in conjunction with RAMmemory, including but not limited to flash memory (FLASH), programmableread only memory (PROM), and electronically erasable programmable readonly memory (EEPROM).

As used herein, the term “processor-based” microcontroller shall refernot only to controller devices including a processor or microprocessoras shown, but also to other equivalent elements such as microcomputers,programmable logic controllers, reduced instruction set

circuits (RISC), application specific integrated circuits and otherprogrammable circuits, logic circuits, equivalents thereof, and anyother circuit or processor capable of executing the functions describedbelow. The processor-based devices listed above are exemplary only, andare thus not intended to limit in any way the definition and/or meaningof the term “processor-based”.

The devices 100 also include sensors 154, 156, 158 provided in a number1 through n that equal the number of switching poles in the device 100.As such, for the three pole device 100 shown in FIGS. 1 and 2, threesensors of each type may be included that respectively detect current,voltage and temperature at respective locations in the device to assessactual operating circuit conditions in the device. Additionaltemperature sensors may optionally be provided per switching pole infurther embodiments for enhanced temperature monitoring at a pluralityof location in each pole. The sensors 154, 156 and/or 158, in turn,provide inputs to the processor 150. Thus, the processor 150, by virtueof the sensors 154, 156 and/or 158, is provided with real-timeinformation regarding current passing through each of the solid statedevices 162 in number 1 through n that equal the number of switchingpoles in the device 100.

The detected current is monitored and compared to a baseline currentcondition, such as a time-current curve or time-current profile that isprogrammed and stored in the memory 152 or the trip unit 160. Bycomparing the detected current with the baseline current condition,decisions can be made by the processor 150 to control the solid stateswitching elements 162, by controlling an output voltage to thegate-emitter voltage in the IGBT's described above, to cease conductingcurrent to protect the load-side from damaging currents. In someembodiments, the trip unit 160 allows the user to select settings forthe operation of the trip unit 160 and alter the time-current responseof the device 100 within predetermined limits. As one such example, auser may select a current rating of the device 100 at a value from 50Ato 100A, with the trip unit 160 applying the appropriate time-currentcurve for the selected current rating.

The detected voltage may likewise be monitored and used to make controldecisions whether to operate the solid state switching elements 162 toprotect the load-side circuitry and components from adverse operatingconditions. Since voltage and current are related, detected voltage canbe compared to detected current to facilitate an assessment of thehealth of the device 100, identify errors, and facilitate diagnosis andtroubleshooting of the electrical power system. As other failsafemeasures, voltage and current can be calculated from sensed parametersand compared to the sensor feedback to detect error conditions.

The detected temperature may likewise be monitored and used to makecontrol decisions whether to operate the solid state switching elements162 to protect the load-side circuitry and components from adverseoperating conditions. Additionally, the detected temperature may ensurethat conductors in the device 100 are operating below rated temperaturesfor the particular hazardous location in which it resides. For example,if the rated temperature is 200° F., the processor 150 can operate thesolid state switches to disconnect and cease current flow when theoperating temperature as indicated by the temperature sensors has risento near 200° F. that could ignite airborne gases, vapors or substancesin NEC Division 1 or 2 locations or IEC Zone 1 or 2 locations.

The processor 150 is in communication with the input/output display 116to provide feedback to a user and to accept inputs made via the display116.

In the example shown, the processor 150 receives line-side power throughpower converter circuitry 162. The power converter circuitry 162includes step down components and analog to digital conversioncomponents when necessary to supply direct current (DC) power to theprocessor 150 at reduced voltage in a known manner. Conversion of theline power to appropriate levels to power the electronics avoids anyneed for an independent power supply, such as batteries and the like ora separately provided power line for the electronic circuitry andcontrols that would otherwise be necessary, although in some embodimentssuch an independent power supply may indeed be included if needed or asdesired. The controls described may be implemented on a circuit board orcircuit boards in various arrangements of electronic packages, withalgorithmic control features programmed and stored in the device memory.

A communication element 164 is also included that may communicate datato a remote location, as well as other device 100 as described furtherbelow to assess operation of the larger electrical power system in localand remote locations relative to any particular device 100. Wireless andnon-wireless communication of data of interest, including but notlimited to current data, voltage data (including waveform data),temperature data, on-off status data of the solid state switchingelements, selected setting data, trip time data, etc. is possible, andsuch data may be stored and archived locally and remotely for analysisof the electrical power system over time. Remote actuation of the device100 is also possible via the communication element 164.

While an exemplary architecture of the device 100 has been described, itis understood that certain elements shown in FIG. 3 may be consideredoptional to provide more basic functionality. Moreover, additionalelements could be added to realize still further sophistication andintelligence in the operation of the device 100, as well as to provideadditional functionality beyond circuit protection and disconnectionfunctionality.

The solid state device 100, because it does not include mechanicalswitch contacts to connect and disconnect the load-side circuitrythrough the device 100, is generally incompatible with conventionalsafety lockout or safety tagout features commonly employed inmechanically actuated switch devices to ensure that disconnection ismaintained while workers are performing maintenance or service tasks onthe load-side of the device 100. Safety lockout or safety tagoutfeatures avoid risks of possible electrocution to workers by preventingre-connection of the load-side circuitry through the device 100 exceptwhen proscribed procedures are followed.

As conventionally implemented, mechanically actuated disconnect devicesare physically locked out via a padlock or other mechanical lockingdevice in manner that physically prevents the closure of themechanically actuated disconnect device pending completion of themaintenance or service tasks to ensure worker safety on the load-side ofthe device. Typically, access to a mechanical unlocking device, such asa key or special tool needed to unlock the device and allow reclosure ofthe mechanical switch contacts in the device is conventionallyrestricted only to a particular person or persons having supervisoryauthority and specific training in properly completing a safety tagoutprocedure to unlock the device for reclosure of the circuitry.

Likewise, and as conventionally implemented, in some cases a number ofphysical locks are used in combination to mechanically lockout aconventional mechanically actuated switch device in an opened positionto prevent the mechanical switch contacts from being reclosed whilemaintenance and service procedures are being performed. Each of thephysical locks provided may only be unlocked or tagged out by adifferent person with a unique key, such that a combination of personsis needed to remove all of the locks before the device can be reclosed.Such conventional safety lockout/tagout procedures using physicallocking devices are effective to ensure that unintentional orinadvertent closure of a conventional mechanically actuated devicecannot be made while maintenance and service tasks are being completed.

The device 100, via the elimination of mechanically actuated switchcontacts of conventional devices, accordingly requires newlockout/tagout features and associated safe mode of operation to providea commensurate degree of lockout/tagout safety assurance to ensureworker safety and manage ignition risks in a hazardous location. Thedevice 100 therefore includes a lockout component, represented aslockout 166 in FIG. 3. The lockout component 166 may, as described next,correspond to one or more lockout components that may respectively bemonitored by the processor 150, implemented electronically via theprocessor 150 and device controls, or assisted or confirmedelectronically through the processor 150 and controls of the device 100.

While the lockout component 166 and corresponding lockout components aredescribed below in the context of and in combination with the device100, which unlike conventional devices is advantageously designed torealize enhanced safety while operating in hazardous locations, thebenefits and advantages of the lockout components described hereinextend more generally to other types of switching disconnect devices andend-use applications that pose similar electrocution risks or ignitionrisks in the maintenance and service of electrical loads and load-sidecircuitry that either require safety lockout or safety tagout features,or render safety lockout/tagout features and procedures desirable.

As such, the device 100 including the inventive lockout componentsdisclosed herein is provided primarily for the sake of illustrationrather than limitation. The lockout components described herein may begenerally employed in any circuit protection device or disconnect devicedesired for the purpose of meeting applicable standards and regulationsrelating to worker safety in and around an energized electrical powersystem. Such standards and regulations may include, for example only,OSHA safety requirements for “Control of Hazardous Energy” (29 CFR1910.147) and NFPA standards 70E and 79 providing guidance to verifythat any stored energy has been properly eliminated or controlled toensure personnel will not be injured or come in contact with electricalor mechanical energy when performing tasks. Remote actuation of circuitprotection devices, disconnect devices and switching devices createsadditional risk that a service person could be electrocuted in theabsence of a lockout device, so it is imperative that the lockoutprovisions prevent all opportunities for energization of the circuitregardless of input type.

FIG. 4 is a front view of the circuit protection device 100 illustratingexemplary safety lockout components that may be used separately or incombination to realize secure safety lockout features and functionality.FIG. 5 is an end view of the circuit protection device 100 with theexemplary safety lockout components engaged. FIG. 6 is an end view ofthe circuit protection device 100 in the connected state with theexemplary safety lockout features disengaged. By virtue of the lockoutcomponents and features provided, the device 100 may securely be held ormaintained in the off or disconnected state via the lockout componentswith the load-side circuitry electrically isolated from the line-sidecircuitry by the solid state switches in the device 100. While thedevice 100 is in the lockout state, mode or condition, unless proscribedtagout procedures are followed the device 100 cannot be inadvertentlyturned back on to its connected state while workers are performingneeded tasks on the electrical loads and load-side circuitry connectedthrough the device 100. Safety assurance is therefore provided that thedevice 100 stays disconnected pending completion of maintenance andservice tasks on the load-side of the device 100.

As shown in FIGS. 4-6, the front face 180 of the device 100 includes thedisplay 116 and a mechanical toggle switch 182 adjacent to the display116. In contemplated embodiments, either the display 116 or the toggleswitch 182 may be utilized to achieve an on/off change of state of thesolid state switching elements in the device 100, although in someembodiments the device 100 may alternatively be provided with one or theother, but not both of the display 116 and the toggle switch 182.

The mechanical toggle switch 182 may be selectively positionable on thefront face 182 of the device between designated “on” and “off”positions. More specifically, the mechanical toggle switch 182 in theexample shown may be rotated back and forth a bit less than 180°(although embodiments are contemplated wherein a toggle switch mayrotate about 90° or even less) from one another about an axis ofrotation of the mechanical toggle switch 182 between the designated onand off positions. The “on” position in a contemplated example is shownin FIG. 6 and in phantom in FIG. 5, while FIGS. 4 and 5 show the toggleswitch 182 in the “off” position. The toggle switch 182 serves as anintuitive and easily used mechanical input selector for a user to turnthe device on or off as desired while also providing visual indicationto the user based on the position of the mechanical toggle switch 182whether the device 100 is on or off

The mechanical toggle switch 182 mimics an on/off operation of knowndevices including a similar toggle switch input selector, but withoutany mechanical actuation of switch contacts. As such, a repositioning ofthe mechanical toggle switch 182 in the device 100 does not cause anymechanical actuation of mechanical switch contacts as none are providedin the device 100. Additionally, a repositioning of the mechanicaltoggle switch 182 does not directly operate the solid state switches inthe device 100 to effect a desired off (disconnection) or on(connection) function. The mechanical toggle switch 182 serves insteadonly as a user input to the electronic controls of the device 100 toachieve electronic change of state of the solid state switches insidethe device 100 to achieve the desired on/off or connect/disconnectfunctionality. Based on the position of the toggle switch 182, which maybe sensed, otherwise detected or communicated to provide a control inputto the processor 150 (FIG. 3). The processor 150 or a device controlleris responsive to the toggle switch position to apply (or not) sufficientgate-emitter voltages to the solid state switching elements to conductelectrical current (or not) and realize the desired on or connectedstate, or alternatively the desired off or disconnected state dependingon the position of the toggle switch.

The mechanical toggle switch 182 may be safely locked out at a distalend thereof in the off position to an anchor element 184 provided in thedevice 100 and projecting upward from the front face 180 adjacent to thedistal end of the toggle switch 182 when in the off position.Specifically, the distal end of the toggle switch 182 may include afirst lock aperture 185 (FIG. 6) that aligns with a second lock aperture186 (FIGS. 5 and 6) of the anchor element 184. When the lock apertures185, 186 are aligned, a locking element such as, for example, a shank188 of a padlock 190 (shown in phantom in FIGS. 4 and 5) may be insertedthrough the aligned lock apertures 185, 186 to physically lock themechanical toggle switch 182 in the off position. The locked mechanicaltoggle switch 182 is an effective safety lockout of the device 100 toensure that the device 100 remains in the disconnected stateelectrically isolating the load-side of the device 100 from theline-side circuitry.

The anchor element 184 may be provided as a metal plate or reinforcedplastic element in contemplated embodiments that is securely mounted tothe device 100 and has sufficient structural strength to resist anyattempt to remove the lock by force. More than one anchor element 184may be provided as desired to improve the lockout arrangement further.While an exemplary anchor element 184 is shown and described, otheranchor elements are possible in further and/or alternative embodiments,with the end result being secure locking of the on/off input selector inthe off position to prevent the device 100 from being turned back on.

By virtue of the exemplary toggle switch 182 and anchor element 184, thedevice 100 may be safely locked out as described above to ensure thatthe device 100 to ensure the safety of workers attending to load-sidemaintenance procedures. The padlock 190 may be opened to unlock thetoggle switch 182 only by an authorized person having a key, such that aperson without the key cannot turn the device 100 on via the toggleswitch 182 that is locked in the off position. While a toggle switch 182and padlock 190 are described and illustrated to obtain a simple lockingarrangement, on/off input selectors other than toggle switches andlocking elements other than padlocks could likewise be utilized withsimilar effect to realize a mechanical lockout for the otherwisenon-mechanical nature of the solid state device 100 in the switchingdisconnect operation.

As mentioned, the mechanical toggle switch 182 may be utilized as astand-alone on/off switch input selector including safety lockoutcapability described, or may be used in combination with the display116. When the toggle switch 182 and the display 116 are each provided,the display 116 may provide visual user feedback to the user when thetoggle switch 182 is being moved between the on and off positions andprovide another visual cue to a user regarding the state of the deviceas being on/connected or off/disconnected. Specifically, when themechanical toggle switch 182 is moved to the on position, the processor150 can operate the solid state switches to conduct current, confirmthat current is being conducted via the sensors provided in the device100, and cause an ON indicator to be presented on the display 116 toconfirm to the user that the device 100 is actually on. Also, when themechanical toggle switch 182 is moved to the off position, the processor150 can operate the solid state switches to become nonconductive,confirm via the sensors provided in the device 100 that the load-sideterminals are electrically isolated, and cause an on OFF indicator to bepresented on the display to 116 confirm to the user that the device 100is actually off.

When confirmation is provided to the user of the actual on or off stateof the device 100, additional safety is provided in the event of adevice control malfunction or a solid state switch malfunction. In sucha scenario, the mechanical toggle switch 182 may be moved to the offposition but the solid state switches remain “on” to conduct current tothe load-side. The display 116, in response to such a condition, whichcan be detected with the load-side sensors on the device 100, canprovide a clear warning on the display 116 that the device 100 is notactually “off” as the user intended via moving the toggle switch 182 tothe opened or off position. Alerts and notification may also begenerated of an error condition for the device 100, and if needed, theline-side circuitry can be electrically isolated, locally or remotely,via operation of an upstream switch device in the electrical powersystem to ensure worker safety in completing needed, load-side tasks.

While confirmatory on/off status indication is described via the display116, indicator lights and other confirmation/feedback features may alsobe utilized to provide confirmation to the user of the actual state ofthe solid state switches as on or off, or to effectively warn users ofdetected device errors or malfunction, either in addition to or in lieuof the display 116. Audio alert features may be provided in someembodiments as enhanced confirmation or warning features using verbalmessages such as “Device On”, “Device Off” or “Warning, Device RemainsOn”, “Warning, Device Remains Off”. Confirmation or warning datamessages may also be automatically generated and communicated to remotedevices for system level assurance, analysis and record keeping purposesto log connections and disconnections made through the device, time ofconnection and disconnection, sensor and mechanical toggle switchstates, or other data of interest.

In embodiments that do not necessarily include the mechanical toggleswitch 182, the display 116 may be touch sensitive and may define anon/off button 192, a safety lockout button 194, and a lockoutdeactivation element 196. The on/off button 192 may be used for ordinaryon/off change of state operation of the device 100 with the controls ofthe device 100 accordingly controlling the solid state switches withoutrequiring the toggle switch 182 or other mechanical input selector.Audio and/or visual feedback may be provided to the user confirming thatthe device 100 is actually on or off, or that an error has been detectedin which a warning is appropriate.

When the display 116 is touch sensitive, graphical icons may be providedin a home screen display and in successive displays as users make inputselections, and user interface selections may be provided in menus orsub-menus. A home screen button may be provided adjacent the display116, and the on/off switch may be provided on the home display forconvenient access. Users may touch, swipe, or utilize other forms ofcontact in operating the display 116 in the style of other types ofsmart devices (e.g., smart phones or tablets) in an easy to usedisplay-driven interface. When a user turns the device 100 off via theon/off input selector in the home screen, another screen display may bepresented that includes the safety lockout button 194. Likewise, whenthe safety lockout button 194 is activated, another screen display maybe presented that includes the lockout deactivation element 196.Numerous variations are possible in this regard.

When the mechanical toggle switch 182 is provided in addition to thedisplay 116, a separate or independent on/off button 192 in the display116 may be considered optional and need not be included. The display 116could automatically switch to different screen displays including the onor off confirmation as the mechanical toggle switch 182 is moved to itson or off positions so that the user can see the device 100 respondingto the user selected position of the mechanical toggle switch 182. Thetoggle switch 182 could be disabled from the controls perspective whenthe lockout is activated as further assurance that it could not be usedto turn the device back on until an electronic lockout condition isproperly deactivated per the discussion below.

In contemplated embodiments wherein the display 116 is not touchsensitive, additional input selectors can be provided in button form orany alternative form desired for users to select or make on/off inputs,a safety lockout input, and a lockout deactivate input, eitherindependently from or in combination with the display 116. Incontemplated embodiments, the additional input buttons may bemultifunctional and may be coordinated with screen displays forintuitive device operation by a user in home screen and related screensto select different options, in a menu-driven user interface, or theinput buttons may be provided with labels and the like may be providedon the device with each input button serving only one purpose only(e.g., on/off selection).

When desired, the safety lockout button 194 (or corresponding inputselector) may be manipulated by a user to activate an electronic lockoutfeature wherein the on/off button 192 (or other corresponding inputselector including but not limited to the toggle switch 182) isdisabled, such that any further user manipulation of the on/off button192 (or other corresponding input selector) is ineffective to change thestate of the solid state switches in the device 100. As such, while thedevice 100 is off and while the lockout is enabled, any attempt by theuser to turn the device 100 back on via an on/off input selector will beignored by the device controls. As before, the actual change of state ofthe solid state switches in the device 100, as detected by the sensorsin the device 100, may be visually confirmed for the benefit of theuser, and safety warnings or error notifications can be made via thedevice 116 concerning possible error conditions or malfunction of thedevice 100. The display 116 may also visually indicate to the user thatthe lockout has been activated, and audio confirmation may be providedas well.

Once the lockout button 194 is activated on the display 116, the device100 remains in the lockout state and may not be turned back on until thelockout deactivation element 196 is correctly used to tagout the lockingelements and deactivate the lockout feature. In one example, when thelockout deactivation element 196 is selected by the user, a screen ispresented to the user to enter a tagout passcode. Of course, incontemplated embodiments the tagout passcode would be known only to adesignated person or persons authorized to turn the device back on andtherefor reclose the device for resumed operation of the power system onthe load-side of the device 100. Unless the proper tagout passcode ispresented, the lockout will not be deactivated, and the on/off inputselector will continue to be disabled and any use thereof to attempt toturn the device on will be ignored.

Such exemplary lockout activation and tagout deactivation features,implemented electronically though the display 116 and the controls ofthe device 100, can complement the toggle switch lockout described aboveor be used as a stand-alone feature. While a passcode deactivationfeature has been described for the electronic lock, other known featuresto verify an authority of a person or known and may be utilized,including but not limited to known biometric elements to identifyfingerprints and the like of an authorized person to unlock the deviceinterface and/or to deactivate a safety lockout.

When the mechanical toggle switch 182 and the display 116 are eachpresent in the device 100, enhanced lockout/tagout procedures arepossible with even greater safety assurance than possible if only one ofthem is provided. For instance, one person may be required to unlock theelectronic feature implemented through the display 116 with the requiredpasscode, and another person may be required to unlock the padlock 190with the required key to release the otherwise locked toggle switch 182so that it can be moved to the on position to turn the device 100 backon. If the mechanical lock is disabled to release the toggle switch 182,but the electronic lock remains activated (or vice versa), the controlsin the device 100 will not allow the device to be turned back on. Such amulti-step lockout/tagout procedure involving different persons isadvisable in a hazardous location to reduce any likelihood of humanerror in operating the switch and therefore increases worker safety andpossible ignition concerns if the device 100 is turned back on beforemaintenance and service tasks are completed on the load-side of thedevice 100.

As still another lockout component providing lockout/tagout safetyassurance, the front face 180 of the device 100 also includes a pair oflockout openings 200, 202 that are respectively shaped, dimensioned andspaced from one another to receive a physical, mechanical lockingelement such as a shank 204 of a padlock 206 (shown in phantom in FIGS.4 and 5) passing through and between each lockout opening 200, 202. Lockdetention sensors 208, 210 (shown in phantom in FIG. 5) are provided todetect the insertion of the locking element (e.g., the shank 204), andwhen insertion of the shank 204 is detected the controls of the device100 can disable the on/off input selector to assume a lockout state orcondition. Therefore, the mechanical act of inserting the shank 204 by auser serves as an electronic control input via the lock detentionsensors 208, 210 that, in turn, cause the device 100 to assume a safetylockout state.

The lock detection sensors 208, 210 in contemplated embodiments may beoptic sensors or limit switches in contemplated examples, although othertypes of sensors are possible in further and/or alternative embodiments.Optionally, the lock detection sensors 208, 210 may be controlled sothat power is supplied to them only when the on/off switch is in the“off” position, therefore avoiding unnecessary power consumption whilethe device 100 is turned on with the on/off switch in the “on” position.As such, the lockout can only be activated via insertion of the lockafter the device 100 has been turned off. This prevents a potentiallyproblematic lockout activation while the device 100 is on and aresultant locking out or preventing a user from turning the device off100 without going through the proscribed lockout deactivation first,which may only be completed by certain users for the reasons above.While a lockout of the device 100 in the on state could in some casesprovide a desirable security feature protecting critical loads frombeing inadvertently turned off by unauthorized persons, such a lockoutto ensure that the device remains on or connected is an optional featurein some embodiments, although in certain instances is undesirable.Specifically, when operating in a hazardous location, the ability toquickly turn the device 100 off and disconnect the load-side whenneeded, without restriction and without time delay to deactivate thelockout(s) provided, is important and should not be impeded, such thatsafety lockout components are typically reserved only for thedisconnected or off state of the device 100 in a hazardous location.Provided that a sufficient emergency over-ride or lockout bypass featurewas present, however, to permit the device 100 to be readilydisconnected even if it had been desirably locked in the on or connectedstate, such a lockout in the on state may be permissible.

Once the lock detection is made by the sensors 208, 210 the device 100remains disconnected in the lockout state with the on/off input selectordisabled as long as the lock remains in place. The padlock 206 may beopened to remove the shank 204 only by an authorized person having akey, such that a person without the key cannot remove the shank 204.Removal of the shank 204 by a designated person is likewise detected bythe sensors 208, 210 causing the device controls to deactivate thelockout and allowing the device 100 to be turned on again via the on/offinput selector.

The automatic lock detection and associated lockout/tagout feature canbe used as a stand-alone feature or in combination with one or both ofthe mechanical toggle switch and electronic display-driven lockoutfeatures described above. Confirmation and user feedback of successfullockout operation, as well as notifications of errors or malfunctionscan be provided as described above. When all three of the lockoutfeatures described are provided in combination, a redundant, three-steplockout/tagout procedure is facilitated that may involve three differentpersons to disable each type of lockout provided. The automatic lockdetection and safety lockout/tagout feature can likewise be providedwith either one of, but not both, of the other features described aboveto facilitate a two-step safety lockout/tagout procedure that mayinvolve two different persons disable each lockout provided.

While exemplary mechanical and electronic safety lockout/tagoutcomponents and methods have been described and illustrated, furtheradaptations are possible. For example, mechanical locking elements otherthan padlocks may be utilized to lock a mechanical input selector suchas the toggle switch 182 in the off position and/or inserted throughlock openings in the device 100. Likewise, other types of lock detectionsensors may detect other types of mechanical locking elements. Variousforms of electronic lockouts may be provided using different userinterfaces and security features to ensure that safety lockouts aresuccessful for the solid state device 100 that do not includemechanically actuated switches, while ensuring that the safety lockoutsmay be deactivated only by authorized persons, and also ensuring thatadditional ignition concerns of hazardous locations are adequatelyaddressed in the operation of the device 100.

FIG. 7 is an exemplary algorithmic flowchart of safety lockoutactivation and deactivation processes 230 for the device 100. Thealgorithmic processes may be implemented, for example, by theprocessor-based controls including the processor 150 and the applicablesensors included in the device controls, or by equivalent controllers inview of the various sensors provided to detect the state or position ofmechanical or electronic input selectors as they relate to voltage orcurrent readings at different locations in the device, and otherconsiderations discussed below.

At step 232, an on/off input element is monitored in the device 100,such as the toggle switch 182 (FIGS. 4-6) or other input selector. Atstep 234, it is determined whether the on/off switch is in the offposition as an input selection of user intent to turn the device 100 offto effect the disconnection of the load-side circuitry and electricalloads through the device 100. When non-mechanical input selectors areprovided, at step 232 the activation of the input elements may bemonitored as the user selects them to change the state of the devicefrom on to off, or from off to on.

If the on/off input element is not in the off position at step 234, thealgorithm returns to step 232 and continues to monitor the on/off inputelement. Unless the on/off input selector is determined to be “off”, itmay be assumed that normal “on” operation of the device 100 connectingthe line-side and load-side circuitry through the device 100 is desiredand no further action is required.

If the on/off input selection is determined to be “off” at step 234, thedevice proceeds to operate the solid state switches at step 236 tobecome nonconductive, such that current can no longer flow through thesolid state switches to the load-side terminals and the desireddisconnection is realized. For purposes of step 236, operation of thesolid state switches refers to the operational controls and actionsneeded to affect the change of state from a current conducting state toa non-current conducting state of the solid state switches provided. Forexample, the operation of the solid state switches refers to thenecessary voltage change to the gate-emitters of the solid stateswitches to reach the non-conductive state of each solid state switch.

At step 238, the processor 150 may confirm whether the load-sideterminals of the device 100 are actually electrically isolated andde-energized via the sensors provided in the device 100. For instance,the load-side terminals of the device 100, if truly isolated as desired,will have zero voltage and zero current detections from the applicablesensors. If non-zero voltage and current is found to exist, theload-side terminals of the device 100 are not isolated as intended, andat step 266 the processor may generate a notice or alert to a local userinterface (e.g., the display 116 described above) and any pertinentremote user interfaces. At step 268, feedback to the user is provided tovisually show the user that the device 100 remains on and not off. Auser observant to the feedback provided will therefore see that there isa problem with the device 100 that needs attention in order for theload-side circuitry to actually be turned off as intended.

If the processor 152 confirms that the load-side terminals of the device100 are actually electrically isolated and de-energized at step 238, aprompt may be presented on the local user interface (e.g., the display116) whether a safety lockout is desired at step 240. If no, thealgorithm returns to step 232 and may continue to check to see if theisolation is maintained. The algorithm therefore acknowledges that attimes disconnection may be desired, but no safety lockout is needed asthe disconnection was not made in view of maintenance or service tasksto be performed on the load-side. The prompt at step 240 also remindsthe user that safety lockout is available if needed, but requiresactivation by the user.

If the safety lockout is desired at step 240, at step 242 the user maybe presented a lockout instruction, such as, for example, to insert andinstall a locking element as described above with respect to theexemplary padlocks. Step-by-step lockout instructions may be provided inthe case where multiple and different types of lockout components areprovided. At step 244, the installation of the lock as instructed may bedetected, and in response to the detection the on/off input element maybe deactivated or disabled to render the on/off input elementnon-responsive to actually turn the device 100 back on and effect thechange of state of the solid state switch elements. At step 248,confirmation may be provided to the user that the safety lockout issuccessfully activated. Workers may therefore safely proceed to performtasks on the electrical loads and load-side circuitry.

At step 250 the device awaits completion of the load-side proceduresbeing performed, continues to confirm that electrical isolation ismaintained, and provides confirmation of the lockout activation.Instruction may be provided at step 252 to the user regardingdeactivation of the safety lockout in order to turn the device back on,including the removal of any mechanical locks or deactivation ofelectronic locks. Step-by-step lockout deactivation instructions can beprovided for each type of lockout component provided in the device 100.

At step 254, a mechanical lock removal may be detected. At step 256 auser validation or authorization to disable any electronic locks isreceived, such as the aforementioned passcode. If at step 258, thevalidation received is determined to be authorized, at step 260 thedeactivation of the safety lockout event is logged. At step 262 theon/off input element is reactivated. The user may now reclose the devicewith the on/off input element, and in response the device controls willoperate the solid state switches to become conductive and re-connect theload-side circuitry through the device 100.

If at step 258, the validation received is not authorized, a notice oralert is generated to remote devices and persons that a possibleimproper attempt to reclose the device 100 was made. Investigation ofsuch occurrence may therefore be made.

Depending on the type and number of lockout components and featuresprovided in the device 100, appropriate modification of the algorithmand processes shown and described are now believed to be apparent.Certain steps as shown and described would not be performed if certainof the lockout types described above were not provided in the device100. Likewise, further steps could be undertaken to accommodateadditional types of lockouts as desired or additional lockout features.While specific examples of processes are therefore set forth above inrelation to exemplary embodiments, similar effect and benefits couldotherwise be realized using other equivalent processes to accommodateadditional or alternative mechanical locking features, various types oflocal and remote user interfaces, various different types of sensors todetect mechanical locking elements, and various forms of userauthorization and validation.

FIG. 8 is a perspective view of a compliant, explosive location circuitprotection device 300 according to another exemplary embodiment of theinvention. The circuit protection device 300 includes the housing 102described having the chemical resistance, impact resistance and thermalmanagement features described above in relation to the device 100, butomits the digital display 116 of the device 100 (FIG. 1). As shown inFIG. 8, a mechanical toggle switch 302 is accessible to a user on theupper front face of the housing 102 for manual activation of the device300 between “on” and “off” states to connect and disconnect theload-side of the device 300 from the line-side. Manual actuators otherthan toggle switches may be employed in other embodiments. In somecases, the display 116 could be provided in addition to or in lieu ofthe toggle switch 302 or another manual actuator. Any of the safetylockout features described above may be employed in the device 100,separately or in combination.

Like the device 100, the device 300 may interconnect line-side or powersupply circuitry and electrical loads operating via alternating current(AC) or direct current (DC). The device 300 as shown is configured as acircuit breaker and therefore provides automatic circuit protection inresponse to predetermined overcurrent conditions, which may be selectedby the user within a certain range and input to the device a local orremote user interface, or otherwise pre-programmed into the device. Thedevice 300 may operate according to specified time-current curves ortime-current profiles suitable to provide adequate protection forconnected loads.

FIG. 9 is a simplified schematic diagram of the circuit protectiondevice 130 in an exemplary hybrid configuration. The device 300 includesinput terminals 130 a, 130 b, 130 c each connected to one phase of athree-phase power supply indicated as line-side circuitry 132 viaconnecting cables or conduits. The device 300 further includes outputterminals 134 a, 134 b, 136 c providing each connected to load-sidecircuitry 136 such as motors, fans, lighting devices, and otherelectrical equipment in an industrial facility wherein ignitable gas,vapors or substances may be airborne as indicated at 138 to produce anexplosive environment.

In between each pair of input terminals 130 a, 130 b, and 130 c, andoutput terminals 134 a, 134 b, and 136 c are mechanical circuit breakers304 a, 304 b, and 304 c and parallel connected solid-state switchdevices arranged as indicated at 140 a, 140 b and 140 c. The exemplarysolid-state switch arrangement 140 a, 140 b, and 140 c includesseries-connected pairs of insulated-gate bipolar transistors (IGBTs)with each pair including a varistor element connected in parallel to theIGBTs as described above. While exemplary solid-state switchingarrangements are shown and described, others are possible to achievesolid-state switching functionality in an arc-less manner. As discussedabove, the solid-state switching devices operate in an arc-less mannerand therefore do not themselves present a risk of ignition insofar asarcing is concerned in a hazardous location.

The combination of the mechanical circuit breakers 304 a, 304 b, and 304c and the solid-state switching arrangements 140 a, 140 b and 140 c canimprove response times of the device 300 relative to that of the device100. The mechanical circuit breakers 304 a, 304, and 304 c however,operate with mechanical switch contacts and accordingly deserve someattention to a hazardous location application as arcing can be anignition source. The solid-state switching arrangements 140 a, 140 b and140 c that are connected in parallel to the mechanical circuit breakers304 a, 304 b, and 304 c can limit the current in mechanical circuitbreakers 304 a, 304, and 304 c in an overload or short circuit event toreduce intensity of any arc produced to a level below that required topresent an ignition concern, or otherwise preclude arcing altogether.

The device 300 may likewise connected to electrical ground 146 todissipate any charging of the housing surface as described above,thereby precluding a possible ignition source via static discharge asdescribed above. In contemplated embodiments, the housing 102 of thedevice 300 may be fabricated from metallic or non-metallic materials. Insome cases involving certain metallic or non-metallic materials,strategic selection of housing materials, filler materials andencapsulant materials is necessary in order to address staticelectricity concerns. Combinations of conductive and non-conductivematerials, both internal to the device 300 and external to the device300 may be utilized to provide paths to electrical ground asappropriate.

The device 300 is likewise connected to an electrical ground 146 todissipate any charging of the housing surface as described above,thereby precluding a possible ignition source via static discharge. Theline and load-side connections may be established using secure terminalassemblies including but not limited to locking terminal features toprevent loosened connections over time after initially being securedwith a fastener, and connections made to enclosed terminals via armoredcable and cable glands to provide enhanced safety assurance forexplosive environments.

FIG. 10 is a block diagram of the circuit protection device 300including, in addition to the elements described above in the device100, control inputs for the manual actuator 302, and a trip actuator 310for operating the mechanical circuit breakers 312 including themechanical switches.

In the case of the device 300, mechanically actuated switch contacts areincluded, and therefore the toggle switch input element 302 which causesthe mechanical switch contacts to open and close may be mechanicallylocked in an opened position to achieve a secure safety lockout for themechanical switch contacts in the device. Confirmation and feedback tothe user may be provided as described above that the mechanical switchcontacts are actually opened to electrically isolate the load-sideterminals. The sensors in the device 300 may also confirm that theelectronic solid state switches are non-conductive and that theload-side terminals of the device are electrically isolated as desired.Error conditions can be detected if the mechanical switch contacts areopened but the electronic solid state switches remain conductive, andwarnings and alerts can beneficially be generated that error conditionsexists or that device malfunction has been detected. Multi-step safetylockout deactivation may be implemented as described above for aredundant degree of safety in which multiple persons are involved indifferent aspects to enhance the safety lockout/tagout procedures andachieve greater safety assurances for operation of the device 300 in ahazardous locations and optionally in non-hazardous locations as well.

When predetermined overcurrent conditions arise, the trip unit 160causes the trip actuator 310 to displace the movable switch contacts andopen the circuit through the device 300. The trip actuator may be anelectromagnetic member such as a solenoid that can simultaneouslydisplace the switch contacts of each mechanical breaker provided in thedevice 300, with the solid-state switching arrangements 140 a, 140 b and140 c limiting the current as the displacement of the switch contactsoccurs. The manual actuator 302 can thereafter be used to reset thedevice 300 by closing the mechanical switches.

While an exemplary device architecture has been described for the device300, it is understood that certain of the elements shown in FIG. 10 maybe considered optional to provide more basic functionality, as well asadditional elements could be added to realize still furthersophistication and intelligence in the operation of the device 300.

FIG. 11 diagrammatically illustrates thermal management features for thecircuit protection device shown in FIGS. 8 through 10. While asdescribed above the hybrid device 300 is capable of operating in anarc-less manner in many instances, but since arcing can depend on thenature of an electrical fault and the voltage and current of theoperating power system at the time of the electrical fault, additionalconsiderations to address any arcing that is realized must beconsidered.

As shown in FIG. 11, and in addition to the thermal management featuresdescribed above in relation to the device 100, the device 300 includesadditional features to ensure that any arcing that occurs in operationof the mechanical circuit breakers is isolated from the ambientenvironment or otherwise is reduced to a level that is insufficient tocause ignition in an explosive location. FIG. 11 illustrates the housing102 of the device 300 defining a first or primary enclosure 320 and aseries of secondary enclosures 322 a, 322 b, and 322 c. The secondaryenclosures 322 serve to contain any electrical arcing within thesecondary enclosure while ensuring that airborne ignitable gases, vaporsor substances cannot reach the secondary enclosures 322 a, 322 b, and322 c and therefore cannot be ignited by operation of the mechanicalcircuit breakers.

In contemplated embodiments, the secondary enclosures 322 a, 322 b, and322 c may be hermetically-sealed chambers that include the respectiveswitch contacts. The hermetically-sealed chambers 322 a, 322 b, and 322c are fluid tight such that any ignitable element of the hazardouslocation that may penetrate the housing 102 into the primary enclosure102 cannot enter the sealed chambers 322 a, 322 b, and 322 c. Thehermetically-sealed chambers may further be vacuum chambers or filledwith inert gas that would reduce arcing intensity and duration, if notavoiding arcing altogether as the switch contacts are opened and closed.Each of the secondary enclosures 322 a, 322 b, and 322 c may be providedwith additional insulation and material to contain any heat associatedwith arcing and localize it to the secondary enclosures 322 a, 322 b,and 322 c inside the larger enclosure 320. The enclosure within anenclosure construction of the housing 102 accommodates the other thermalmanagement features described above, while addressing the additionalconcerns of the mechanical switch contacts in the explosive environment.

The secondary enclosures 322 a, 322 b, and 322 c may be fabricated fromdifferent materials than the rest of the housing 102, or a combinationof materials that may be the same or different from the remainder of thehousing. Metal and plastic materials may be utilized, for example, toconstruct the chambers while the primary enclosure and the rest of thehousing may be entirely plastic. Numerous variations are possible inthis regard. The secondary enclosures 322 a, 322 b, and 322 c may beprefabricated for assembly with the housing 102 at a separate stage ofmanufacture. The secondary enclosures 322 a, 322 b, and 322 c mayenclose some or all of the mechanical circuit breaker mechanism, withoutimpeding the path of motion of the switch contacts or their ability tomove.

Each of the devices 100 or 300 may be safely used in IEC Zone 1 or 2 orNEC Division 1 or 2 hazardous locations, without conventional,separately provided explosion-proof enclosures, and the enhanced safetylogout/tagout features and intelligence as described above in relationto the device 100 apply equally to the device 300. The built-in ignitionprotection features described above either eliminate ignition sources orreduce them levels that are insufficient to cause ignition. The devices100 or 300 are therefore sometimes referred to as beingignition-protected and therefor eliminate any need for a separateexplosion-proof enclosure. As such, the devices 100 and 300 prevent thepossible explosion that the explosion-proof enclosure conventionallyexists to safely contain. The devices 100 and 300 can accordingly safelyoperate in explosive locations and obviate costs and burdens ofconventional explosion-proof enclosures while saving space in theelectrical power system.

FIG. 12 illustrates an exemplary panelboard 400 including compliant,hazardous location circuit protection devices including an array ofdevices 402, 404 arranged as two columns of devices. The devices 402,404 in each column include the devices 100 or 300 described above, andthe devices 402, 404 may be represented in different ratings offeringdiffering degrees of circuit protection to the various different loadsserved by the panel and its various branches. The panelboard 400typically includes its own enclosure, but because of theignition-protected devices 402, 404 that are used on the panelboard itcan be a standard enclosure that is not designed to be explosion-proof.Because the devices 402, 404 are ignition protected, they can reside inthe panel enclosure without conventional explosion-proof enclosures inthe panel enclosure either. The panel enclosure provides some protectionto the devices 402, 404 from environmental conditions, butno-explosion-proofing is needed by virtue of the ignition-protecteddevices 402, 404. Considering that known panelboards may accommodate upto 84 devices, elimination of the separately provided individual andcollective explosion-proof enclosures lowers costs substantially foroperation of the devices 402, 404 in hazardous locations. The costs aremultiplied even further for large electrical power systems including anumber of panelboards located at different locations.

Safety lockout features such as those described above may be implementedon a systems level in the panelboard assembly. For example, a separateuser interface could be supplied in relation to the panel, andmechanical and electronic lockouts of the type described above may beadopted to act upon or through the panelboard user interface todisconnect all of the devices 402, 404 as a group and lockout all of thedevices 402, 404 in the group via the panelboard user interface whendesired, eliminating any need that may otherwise exist to individuallydisconnect and lockout each of the devices 402, 404. Likewise, groupdeactivation of safety lockout features is possible, and groups of thedevices 402, 404 may be collectively turned back on via the panelboarduser interface. Also, such a panelboard user interface may collectivelyshow the on/off status or lockout status of each device 402, 404 singlyor in groups. To the extent that the devices 400, 402 may be desirablyused individually to disconnect only selected ones of the connectedelectrical loads through the individual devices 402, 404 in the panel,the panelboard user interface may likewise present status andconfirmation of the state of the devices 402, 404. For example,considering n circuits connected through the panel, circuits 1, 7, 12and 19 in the panel may be locked out via the selected devices 402, 404with a single lock (implemented through the panel rather than theindividual devices), simultaneously preventing the devices from beingclosed to energize circuits 1, 7, 12 and 19.

The thermal management concerns of device operation in a hazardouslocation are further multiplied in such a panelboard installationincluding numerous devices 402, 404 operating simultaneously and inclose proximity to one another. Heat effects can accumulate and adjacentdevices may run hotter (i.e., with higher surface temperatures) thanthey would if used individually, or at least spaced farther apart fromone another. When the panelboard includes an enclosure, withoutnecessarily requiring an explosion-proof enclosure, the devices 402, 404in the upper portions of the columns may further run hotter than devices402, 404 in the lower portions of the enclosure as the heat rises fromthe lower situated devices 402, 404. In some instances then, activecooling features and systems may be advisable to avoid undesirabletemperature effects on the operation some of the devices 402, 404 or toaddress elevated surface temperatures. As mentioned above, an activecooling system could be provided on or in relation to the panelboard tocool devices 402, 404 at a systems level, as opposed to individually.Variations and combinations of active cooling elements and systems arepossible to achieve different cooling effects. The active cooling systemcould be triggered by ambient temperate sensing, temperature readingsfrom any of the temperature sensors provided in the devices 402, 404, orin view of other factors and consideration to run only on-demand asactually needed, or may alternatively be run continuously orintermittently as needs dictate.

While a panelboard and panelboard enclosure are described above for thedevices 402, 404, similar benefits may be realized in motor controlcenters and other locations in an electrical power system whereincircuit protection devices 402, 404 are likewise conventionally locatedin non-explosion-proof enclosures. Considering the sensors andintelligence provided in the devices 402, 404 and motor-inrush featuresprovided in the devices 402, 404 additional motor startup componentscould be integrated in the design of the devices 402, 404 and provide acombination circuit protector/motor starter in a single package, asopposed to conventionally provided, separately packaged and seriesconnected circuit protectors and motor starter assemblies that eachrequire explosion-proof enclosures for use in hazardous locations. Otherdual purpose or dual function devices 402, 404 are likewise possiblethat reduce costs of installing and servicing electrical power systemseven further by reducing the number of devices that need to be acquired,installed, and serviced in the power system.

The solid state or hybrid devices such as those described above may beconstructed using various different solid state switching elements,arrangements of solid state switching elements, and also implemented invarious different power electronics topologies. Various differentembodiments are contemplated involving varying degrees of on-state loss,propensity to arcing in operation, conduction loss, component count,relative complexity, ability to meet specific response timecharacteristics, simplicity or complexity of operating algorithms, andability to integrate motor soft-starting or other features when desired.Solid state switching elements can be connected in series or in parallelto achieve desirable voltage rating scaling or desirable current ratingscaling using modular arrangements. To the extent that by-pass contactsare desirably implemented, encapsulation materials and thermalmanagement features for the by-pass contact(s) provided may beadvisable.

Any of the solid state and hybrid switch arrangements shown anddescribed above may include or be connected to line-side electricalfuses to enhance circuit protection assurance by addressing anydeficiency or the solid state switching elements with respect to certainovercurrent conditions or to improve response times to certain operatingconditions.

The device construction and safety lockout/tagout features describedabove can easily be applied to realize circuit protection devices thatare not circuit breaker devices, but are nonetheless ignition protectedfor use in NEC Division 1 or 2 hazardous locations, as well as IEC Zone1 or 2 locations, without explosion-proof enclosures. For examplefusible switch disconnect devices are discussed above that includemechanical switches in combination with fuses. Applying the chemical andimpact resistant housing constructions, arc-free switching operation,secure terminal assemblies and thermal management features described, asolid-state fusible switch disconnect device or a hybrid fusible switchdisconnect device can easily be constructed with similar benefits, butoffering a different degree of circuit protection.

Likewise, the chemical and impact resistant housing construction,arc-free switching operation, safety lockout/tagout features and certainof the thermal management features described above can easily be appliedto realize switching devices that do not themselves provide overcurrentcircuit protection, but are nonetheless ignition protected for use inNEC Division 1 or 2 hazardous locations or IEC Zone 1 or 2 locations,without separately provided explosion-proof enclosures. For example,mechanical relay switches and contactors are known that providedisconnection functionality without capability to independently operateand protect against overcurrent conditions. Applying the chemical andimpact resistant housing construction, arc-free switching operation,safety lockout/tagout features and thermal management featuresdescribed, a solid-state relay device or a hybrid relay device, and asolid-state contactor device or a hybrid contactor device can easily beconstructed for safe operation in an explosive environment withintelligent lockout detection capability, lockout detection, andconfirmation.

Ignition-protected devices such as those described can be provided withany desired number of switching poles, including for example only singlepole devices, two pole devices, three pole devices, and four poledevices to accommodate the needs of any type of power systems, includingmultiphase power systems and polyphase power systems, while universallyproviding ignition protection for use in NEC Division 1 or 2 locationsor IEC Zone 1 or 2 hazardous locations.

Having described devices and applicable operating algorithmsfunctionally per the description above, those in the art may accordinglyimplement the algorithms via programming of the controllers or otherprocessor-based devices. Such programming or implementation of thealgorithmic concepts described is believed to be within the purview ofthose in the art and will not be described further.

The benefits and advantages of the inventive concepts are now believedto have been amply illustrated in relation to the exemplary embodimentsdisclosed.

An embodiment of a compliant switch device for a hazardous location hasbeen disclosed. The compliant switch device includes an ignitionprotected housing, a line-side terminal and a load-side terminal coupledto the housing, and a bus structure in the housing and including atleast one solid state switching element operable in an arc-free mannerto connect the load-side terminal to the line-side terminal anddisconnect the load-side terminal from the line-side terminal. Theswitch device also includes an on/off input selector to change a stateof the at least one solid state switching element, and a controllermonitoring a state of the on/off input selector, and responsive to achange in state of the lockout input selector the controller isconfigured to activate a safety lockout condition disabling the on/offinput selector and preventing a change in state of the at least onesolid state switching element via the on/off input selector, whereby theswitch device is compliant for use in the explosive environment withoutrequiring a separately provided explosion-proof enclosure.

Optionally, the controller may also be configured to confirm a change ofstate of the at least one solid state switching element, and provideuser confirmation of the changed state. The on/off input selector may bea mechanical input selector, and more specifically may be a mechanicaltoggle switch that is securable in the off position via a mechanicallock element such as a padlock.

As further options, the on/off input selector may be incorporated in anelectronic display. The controller may be configured to deactivate thesafety lockout condition when a predetermined passcode is provided by auser.

Also optionally, the switch device may include a detector that senses apresence or absence of a mechanical lock element for the safety lockout.The detector may be configured to sense a presence or absence of apadlock shank.

Multiple and different types of safety lockout components may beprovided in the switch device. The multiple and different types ofsafety lockout components may be operable in combination to effect amulti-step lockout procedure. The multiple and different types of safetylockout components may include a mechanical toggle switch and a lockopening, a padlock and detector sensing a presence of the padlock, and amultifunctional display.

The switch may also include at least one mechanical switch contact inthe bus structure, and the housing may include a sealed internalenclosure containing the at least one mechanical switch contact, therebyprecluding the switch contact from being an ignition source in theexplosive environment. The at least one at least one solid stateswitching element may be encapsulated. The switch device may be as asolid state overcurrent protection device, or may be configured as ahybrid overcurrent protection device. The housing of the switch devicemay be electrically grounded and/or exhibit anti-static properties. Thehousing may be chemically resistant in the hazardous location.

This written description uses examples to disclose the invention,including the best mode, and also to enable any person skilled in theart to practice the invention, including making and using any devices orsystems and performing any incorporated methods. The patentable scope ofthe invention is defined by the claims, and may include other examplesthat occur to those skilled in the art. Such other examples are intendedto be within the scope of the claims if they have structural elementsthat do not differ from the literal language of the claims, or if theyinclude equivalent structural elements with insubstantial differencesfrom the literal languages of the claims.

What is claimed is:
 1. A compliant switch device for a hazardouslocation, the compliant switch device comprising: an ignition protectedhousing; a line-side terminal and a load-side terminal coupled to thehousing; a bus structure in the housing and including at least one solidstate switching element operable in an arc-free manner to connect theload-side terminal to the line-side terminal and disconnect theload-side terminal from the line-side terminal; an on/off input selectorto change a state of the at least one solid state switching element; acontroller monitoring a state of the on/off input selector, andresponsive to a change in state of the lockout input selector thecontroller is configured to activate a safety lockout conditiondisabling the on/off input selector and preventing a change in state ofthe on/off input selector; whereby the switch device is compliant foruse in the explosive environment without requiring a separately providedexplosion-proof enclosure.
 2. The switch device of claim 1, wherein thecontroller is further configured to confirm a change of state of the atleast one solid state switching element, and provide user confirmationof the changed state.
 3. The switch device of claim 1, wherein theon/off input selector is a mechanical input selector.
 4. The switchdevice of claim 3, wherein the on/off input selector is a mechanicaltoggle switch.
 5. The switch device of claim 3, wherein the mechanicaltoggle switch is securable in the off positon via a mechanical lockelement.
 6. The switch device of claim 5, wherein the mechanical lockelement is a padlock.
 7. The switch device of claim 1, wherein theon/off input selector is incorporated in an electronic display.
 8. Theswitch device of claim 1, wherein the controller is configured todeactivate the safety lockout condition when a predetermined passcode isprovided by a user.
 9. The switch device of claim 1, further comprisinga detector that senses a presence or absence of a mechanical lockelement for the safety lockout.
 10. The switch device of claim 9,wherein detector is configured to sense a padlock shank.
 11. The switchdevice of claim 1, wherein multiple and different types of safetylockout components are provided.
 12. The switch device of claim 11,wherein the multiple and different types of safety lockout componentsare operable in combination to effect a multi-step lockout procedure.13. The switch device of claim 1, wherein the multiple and differenttypes of safety lockout components include a mechanical toggle switchand a lock opening, a padlock and detector sensing a presence of thepadlock, and a multifunctional display.
 14. The switch device of claim1, further comprising at least one mechanical switch contact in the busstructure, and the housing including a sealed internal enclosurecontaining the at least one mechanical switch contact, therebyprecluding the switch contact from being an ignition source in theexplosive environment.
 15. The switch device of claim 1, wherein the atleast one at least one solid state switching element is encapsulated.16. The switch device of claim 1, wherein the device is configured as asolid state overcurrent protection device.
 17. The switch device ofclaim 1, wherein the device is configured as a hybrid overcurrentprotection device.
 18. The switch device of claim 1, wherein the housingis electrically grounded.
 19. The switch device of claim 1, wherein thehousing exhibits anti-static properties.
 20. The switch device of claim1, wherein the housing is chemically resistant in the hazardouslocation.